The invention relates to a process for the preparation of metallocene complexes, in particular the invention relates to a process for the preparation of bridged bis(indenyl)ligands that can be used for the preparation of metallocene complexes, to a metallocene complex obtained or obtainable by said process and to the use of the metallocene complexes thus obtained or obtainable in polyolefin polymerization.
Metallocene complexes with bridged bis(indenyl) ligands have proven to be highly active in the polymerization of α-olefins, such as ethylene after activation with aluminoxane cocatalysts. However, the known syntheses of the ligands used in the synthesis of these metallocene complexes are tedious as they include unstable intermediates and/or require commercially unattractive compounds. Therefore, there is a desire for synthetic routes that make these valuable metallocene complexes easily accessible.
E. G. Ijpeij et al., “A Suzuki coupling based route to 2,2′-bis(2-indenyl)biphenyl derivatives,” J. Org. Chem., 2002, 67, 167 describe a number of processes for the preparation of bridged bis(indenyl) ligands. Many of these rational pathways were not successful and only one reaction leads to the desired ligand precursor 2,2′-bis(2-indenyl)biphenyl. However, the yield of this route obtained by Ijpeij, E. G., et al. for only the last step was only 79%.